Why do trunks of wetland trees often have buttressed bases? Looking for Ideas...

Scene from the Lower Suwannee NWR - click to enlarge

The photo above, made in the floodplain forest of the lower Suwannee River National Wildlife Refuge, shows the trunks of what appear to be at least three kinds of trees. The one in the mid-distance at the center left is clearly a bald cypress (Taxodium distichum). I would need to return to the site to know for sure, but suspect the one only partially shown in the near left is a water tupelo (Nyssa aquatica) and the leaning one in the right foreground is a water hickory (Carya aquatica). What they have in common and with several other kinds of wetland trees is the way the fluted bases of their trunks differ from the mostly circular bases of their upland relatives. Even when the same species may thrive in both wet and dry sites, they may have trunks with mostly round bases in the dry sites and extensive buttressing in wet sites. 


Swollen trunks in wetland trees are believed to develop when flooding causes hormones and nutrients to accumulate near the water line, promoting more rapid growth in that part of the trunk. The fascinating question is not how buttresses are formed, but why they are formed. Nature is rarely wasteful, and unless the energy invested in buttresses produces some advantages for their trees, they likely would disappear.


Any ideas about the significance of these formations--what they do for the trees? I have one, but am interested in what others may think about the value of buttressed trunks. I'll reveal mine in a later post.